Standard marine VHF radio involves line-of-sight communication between stations; once sailors venture far from the sight of land, communication with a standard marine VHF radio is no longer feasible. In order to communicate over long distances, many mariners use high frequency (HF) single side band (SSB) radio, which operates in a frequency range of approximately 2 MHz to 28 MHz. The range of SSB is up to several thousand miles and calls between yachts are free. In most parts of the world, a SSB operator can communicate with the coast guard up to several hundred miles offshore. Using modern SSB equipment, sailors can receive global weather reports via facsimile, and send and receive email.
SSB radio offers security, entertainment and general communications while at sea. In particular, since SSB is a “party line” system where all operators on a given channel can hear each others' communications, it is ideal for coordinating rescues at sea, for offshore ocean race position roll calls, and for marine “nets” where cruisers gather on a schedule to discuss topics of interest.
The strength of transmitted radio signals, and the quality of radio reception, often depends on the performance of the antenna. An oceangoing boat typically carries a dipole antenna using the seawater surface as a reflector. However, boats have stringent space limitations; a straight quarter-wavelength antenna at 2 MHz would be approximately 37 m long and thus impractical for a typical vessel, particularly a sailing yacht. It therefore is desirable to implement an antenna system for SSB radio that is a suitable size while providing usable signal strength and reception quality.